Hi, Konn.
That’s a good question. I don’t have any inside information on it. If I had to guess, I would guess that because the Goodreads Facebook app is a Goodreads product, it doesn’t use the third-party API or isn’t considered a third-party application by Goodreads. Don’t take that as the last word on it, though, because I really don’t know.
As an experiment, I took the ISBN from your shortcode, copied the reviews iframe source directly from an API call through my browser (instead of from the plugin), and pasted that iframe source URL directly into my browser’s location bar. Same result. No reviews. So, for whatever reason, the reviews for that title are not being published through the Goodreads API.
I’m going to go ahead and mark this topic as resolved, just because the issue is an API issue and not an issue with the plugin. Thanks again for using GoodReviews and let me know if I can be of further assistance.
James